1. Field of the Invention
The present invention relates to an injection molding apparatus of the type having a hot-runner mold which moves relative to an injection nozzle of an injection unit, and to blow-molding apparatus using the same.
2. Description of the Prior Art
The Japanese Utility Model Publication No. 58-52914 discloses a blow-molding apparatus in which for each shot of injection-molding the product a hot-runner mold is driven vertically by a mold clamping ram. In this injection molding apparatus, it is not possible, because the hot-runner mold is raised and lowered, to maintain the injection nozzle of the injection unit in constant contact with the sprue of the hot-runner mold. As a result, when raising and lowering the hot-runner mold, it is necessary to withdraw the entire injection unit far enough that the hot-runner mold and injection nozzle do not interfere with each other.
If contact between the injection nozzle and hot-runner mold is lost, not only does leakage of resin occur from both the hot-runner mold sprue and the injection nozzle of the injection unit, but the stability of the molding is also impaired. For example, when the injection nozzle comes back in contact with the hot-runner mold sprue, air is trapped within the runner of the hot-runner mold, and this may lead to molding defects. Furthermore, the molten resin coming into contact with the atmosphere cools and solidifies, or is liable to contamination by air-borne contaminants, so that the flow of the resin is impaired and the molding characteristics worsened. These considerations are a large factor in the reduction of the molding yield.